AsuroImgui/ImguiNodes/ImguiNodes.cpp

//Disables console window
#if !_DEBUG
#pragma comment(linker, "/SUBSYSTEM:windows /ENTRY:mainCRTStartup")
#endif

#include <iostream>
#include <algorithm>
#include "ImguiBase.h"
#include "ImguiNodes.h"

int main()
{
	CustomDrawData customDrawData{};

	startImgui(&customDrawData, init, draw);
}

/// <summary>
/// Setup before first draw.
/// </summary>
void init()
{
	ImGuiIO& io = ImGui::GetIO();
	io.Fonts->AddFontFromFileTTF("Montserrat-Regular.ttf", 16.0f);
}

/// <summary>
/// Draw main application content.
/// </summary>
void draw(DrawData& drawData, void* customDataVoid)
{
	CustomDrawData* customData = static_cast<CustomDrawData*>(customDataVoid);

	bool isDraggingLine = false;
	ImVec2 lineStartPos = ImVec2{};

	// Top menu bar
	ImGui::BeginMainMenuBar();
	if (ImGui::Button("Add Node"))
	{
		std::string name{ "Node " };
		name.append(std::to_string(customData->nodes.size() + 1));
		customData->nodes.push_back(NodeWindow(name));
	}
	ImGui::EndMainMenuBar();

	// Draw all node windows
	auto nodeIterator = customData->nodes.begin();
	while (nodeIterator != customData->nodes.end())
	{
		NodeWindow& node = *nodeIterator;

		bool nodeOpen;
		ImGui::Begin(node.title.c_str(), &nodeOpen, ImGuiWindowFlags_NoResize | ImGuiWindowFlags_AlwaysAutoResize);
		if (!nodeOpen)
		{
			auto triggerIterator = node.triggers.begin();
			while (triggerIterator != node.triggers.end())
			{
				triggerIterator = cleanEraseElement(node.triggers, triggerIterator, customData);
			}
			auto alertIterator = node.alerts.begin();
			while (alertIterator != node.alerts.end())
			{
				alertIterator = cleanEraseElement(node.alerts, alertIterator, customData);
			}

			nodeIterator = customData->nodes.erase(nodeIterator);
			ImGui::End();
			break; // TODO: contine will create problems with closing too many windows?
		}

		// Expand clip rect to allow circles on edges
		ImVec2 contentMin = ImGui::GetWindowPos();
		ImVec2 contentMax = ImVec2{ contentMin.x + ImGui::GetWindowWidth(), contentMin.y + ImGui::GetWindowHeight() };
		ImGui::PushClipRect(ImVec2{ contentMin.x - 15, contentMin.y }, ImVec2{ contentMax.x + 15, contentMax.y }, false);

		auto alertIterator = node.alerts.begin();
		while (alertIterator != node.alerts.end())
		{
			if (drawCircle(0, CircleDragType::Source, alertIterator._Ptr, &alertIterator->position))
			{
				isDraggingLine = true;
				lineStartPos = alertIterator->position;
				ImGui::Text(alertIterator->name.c_str());

				ConnectionPayload payload{ alertIterator->id };

				ImGui::SetDragDropPayload("NODE_CONNECTION", (void*)&payload, sizeof(ConnectionPayload));
				ImGui::EndDragDropSource();
			}

			ImGui::Text(alertIterator->name.c_str());
			if (ImGui::IsWindowHovered() || ImGui::IsWindowFocused())
			{
				if (inlineButton("x", alertIterator._Ptr))
				{
					alertIterator = cleanEraseElement(node.alerts, alertIterator, customData);
					continue;
				}
			}
			alertIterator++;
		}

		auto triggerIterator = node.triggers.begin();
		while (triggerIterator != node.triggers.end())
		{
			if (drawCircle(-ImGui::GetStyle().WindowPadding.x, CircleDragType::Target, triggerIterator._Ptr, &triggerIterator->position))
			{
				if (const ImGuiPayload* payload = ImGui::AcceptDragDropPayload("NODE_CONNECTION"))
				{
					ConnectionPayload* payloadData = static_cast<ConnectionPayload*>(payload->Data);
					
					customData->connections.push_back(NodeConnection { payloadData->sourceID, triggerIterator->id });
				}
				ImGui::EndDragDropTarget();
			}

			ImGui::Text(triggerIterator->name.c_str());
			if (ImGui::IsWindowHovered() || ImGui::IsWindowFocused())
			{
				if (inlineButton("x", triggerIterator._Ptr))
				{
					triggerIterator = cleanEraseElement(node.triggers, triggerIterator, customData);
					continue;
				}
			}
			triggerIterator++;
		}

		if (ImGui::Button("New Alert"))
		{
			node.alerts.push_back(NodeElement("Today, 18:00"));
		}
		if (ImGui::Button("New Trigger"))
		{
			node.triggers.push_back(NodeElement("Doot"));
		}

		ImGui::PopClipRect();
		ImGui::End();
		nodeIterator++;
	}

	// Draw drag line in foreground
	if (isDraggingLine)
	{
		ImDrawList* drawList = ImGui::GetForegroundDrawList();
		drawList->AddLine(lineStartPos, ImGui::GetMousePos(), IM_COL32(200, 200, 200, 255), 3.0f);
	}

	// Draw connected lines in background
	ImDrawList* bgDrawList = ImGui::GetBackgroundDrawList();
	for (NodeConnection& nodeConnection : customData->connections)
	{
		ImVec2 sourcePos = ImVec2{ 0, 0 };
		ImVec2 targetPos = ImVec2{ 0, 0 };
		for (auto node : customData->nodes)
		{
			for (auto alert : node.alerts)
			{
				if (alert.id == nodeConnection.sourceID)
				{
					targetPos = alert.position;
				}
			}
			for (auto trigger : node.triggers)
			{
				if (trigger.id == nodeConnection.targetID)
				{
					sourcePos = trigger.position;
				}
			}
		}
		bgDrawList->AddLine(sourcePos, targetPos, IM_COL32_WHITE, 2.0f);
	}
}

/// <summary>
/// Draws a small circle in the same row.
/// </summary>
/// <param name="outCirclePos">Returns the position of the circle.</param>
/// <returns>True if an event matching the dragType has occurred.</returns>
bool drawCircle(float xOffset, CircleDragType dragType, const void* id, ImVec2* outCirclePos)
{
	auto cursor = ImGui::GetCursorScreenPos();
	ImDrawList* drawList = ImGui::GetWindowDrawList();

	float circleRadius = 5;
	float yCircleOffset = ImGui::GetTextLineHeight() / 2.;
	ImVec2 circlePos = ImVec2{ cursor.x + xOffset, cursor.y + yCircleOffset };

	drawList->AddCircleFilled(circlePos, 5, IM_COL32_WHITE);

	ImVec2 originalPos = ImGui::GetCursorPos();
	ImGui::SetCursorPosX(xOffset);
	ImGui::PushID(id);
	ImGui::InvisibleButton("", ImVec2{ 15, 15 });
	ImGui::PopID();
	ImGui::SetCursorPos(originalPos);

	if (outCirclePos != nullptr)
	{
		*outCirclePos = circlePos;
	}

	if (dragType == CircleDragType::Source && ImGui::BeginDragDropSource())
	{
		return true;
	}
	if (dragType == CircleDragType::Target && ImGui::BeginDragDropTarget())
	{
		return true;
	}
	return false;
}

/// <summary>
/// Draws a small button in the same row.
/// </summary>
bool inlineButton(const char* title, const void* id)
{
	ImGui::SameLine();
	ImGui::PushID(id);
	if (ImGui::SmallButton(title))
	{
		ImGui::PopID();
		return true;
	}
	else
	{
		ImGui::PopID();
		return false;
	}
}

/// <summary>
/// Removes any attached connections before erasing this NodeElement from a vector.
/// </summary>
/// <returns>Continued iterator</returns>
std::vector<NodeElement>::iterator cleanEraseElement(std::vector<NodeElement>& elements, std::vector<NodeElement>::iterator toErase, CustomDrawData* data)
{
	auto connectionIterator = data->connections.begin();
	while (connectionIterator != data->connections.end())
	{
		if (connectionIterator->sourceID == toErase->id || connectionIterator->targetID == toErase->id)
		{
			connectionIterator = data->connections.erase(connectionIterator);
			continue;
		}
		connectionIterator++;
	}
	return elements.erase(toErase);
}

NodeElement::NodeElement(std::string name)
{
	this->id = nodeIdCounter;
	nodeIdCounter++;
	this->name = name;
	this->position = ImVec2{ 0, 0 };
}

NodeWindow::NodeWindow(std::string title)
{
	this->title = title;
	this->alerts = std::vector<NodeElement>();
	this->triggers = std::vector<NodeElement>();
}